Devices such as those described in U.S. Pat. Nos. Re. 30,787 and 4,379,019 are well known for applying a strip of masking tape along one edge of a sheet of masking material with a portion of the tape extending past the edge of the masking material by which the masking material may be temporarily attached along a surface to be protected, such as during painting of an adjacent surface. Typically such devices include a cut off blade by which the tape and sheet of masking material may be severed after a desired length thereof has been withdrawn from the device.
U.S. patent application Ser. No. 116,508 entitled "Sheet Material for Masking Apparatus" filed Nov. 2, 1987, now abandoned, describes a roll of thin polymeric masking material intended for use on the type of device described in U.S. Pat. Nos. Re. 30,787 and 4,379,019, which masking material is a wide sheet folded back and forth upon itself to shorten the length of the roll so that after application of the tape to the masking material and to a surface to be masked the sheet of masking material must be unfolded to obtain the benefit of its full width. The cut off blade normally used in that device, however, does not readily cut the multiple layers of such folded polymeric material, particularly when several folds are present (e.g., over 2 folds).
U.S. patent application Ser. No. 283,237 entitled "Cut Off Blade for Severing Multiple Layers of Thin Polymeric Sheet Material" filed Dec. 12, 1988, now U.S. Pat. No. 4,913,767 describes a cut off blade with a cutting edge portion that is particularly efficient at severing a polymeric sheet of masking material folded in multiple layers. Generally that cut off blade comprises a thin metal sheet including a plurality of similarly shaped teeth providing a cutting edge portion of the blade, each of which teeth defines parts of first and second major surfaces of the blade in the shapes of isosceles triangles having bases adjacent the attachment portion and aligned in a first direction along the blade so that points of the triangular surface parts project at right angles to the first direction. The teeth provided are relatively sharp and long so that with easily applied manual force the teeth can pierce multiple layers of polymeric sheet material (e.g., up to 24 layers) to prevent any of the layers from slipping on the cutting edge, and can then progressively cut through the layers to complete the cut.
While the cutting edge on the cut off blade described in U.S. patent application Ser. No. 283,237 is very effective in cutting layers of polymeric sheet material, its very sharp teeth present the potential for damage to an object with which it comes in contact or injury to a user of the device.